Continuous Variable Gain UWB Low Nosie Amplifiler

In recent years, the Ultra Wide-Band (UWB) technology as a novel wireless communication technology has become a hot research. A low noise amplifier (LNA) is one of the most critical blocks in the receiver front-end of UWB systems, which determines the performance of the whole receiver.So it is very significant to research on UWB LNA.The paper briefly introduces the research status and significance of UWB LNA, and illustrates that it is necessary to design a variable gain UWB LNA firstly.Then the basic theory of low noise amplifier (LNA) is summarized systematically. Finally,a CMOS continuous variable gain UWB LNA is presented.The main achievements of this work consist of following aspects:(1) The current various configurations of UWB LNA including their small-signal model and noise model are analyzed and summarized systematically.Also thier advantages and disadvantages are compared.(2) The existing variable gain methods are introduced and compared.(3) A tow-stage CMOS variable gain LNA (VG-LNA) with large and continuous gain variation for 3-5GHz is presented. A tow-section Chebyshev filter is exploited to achieve excellent input match in the band and to optimize the noise performance. An source-follower is designed specially to match output. By controlling the bias current of the second stage, a continuous gain tuning range of 36dB is achieved without influencing the input match and output match. The VG-LNA shows the following performance at the highest gain:S11and S22 are less than -10.1dB and -15dB respectively, and 23.8dB peak gain, only 1.5dB minimum noise figure,-7dBm input-referred third-order intercept point, while dissipates 6.8 mW from a 1.2V supply.(4)A new CMOS variable gain LNA (VG-LNA) with continuous gain variation for 3-10GHz is presented. With the common-gate configuration and a simple high-pass filter employed as the input stage, the broad-band input matching is obtained. By controlling the bias current of the second stage, a continuous gain tuning range of 19dB is achieved without influencing the input match and output match. Its performance at the highest gain mode is as follows: S11 and S22 are less than -10.3dB and -10.6dB respectively, and 12.4dB peak gain, 3.28dB minimum noise figure, while drawing13.1mA from a 1.5V supply.The proposed circuits are simulated in TSMC RF CMOS 0.18μm technology by ADS2006, and the layout and post-layout simulation are used by Candence. The pre-layout simulation and post-layout simulation results show that it is more excellent than recently published CMOS designs, and the function of continuous variable gain for UWB LNA is achieved.